Hydroquinone manufacture



Patented Jan. 5, 1937 UNITED STATES PATENT OFFICE HYDROQUINONEMANUFACTURE Joseph Schumacher, Peru, Ill., assignor to Garus ChemicalCompany, a corporation of Illinois No Drawing. Application May 9, 1936,

Serial No. 78,921

9 Claims.

product from the borings and turnings' of cast iron cylinder blocks andother castings from the automotive industry. The recent tendency in thisfield is to use alloyed irons and there is also an increasing tendencyto use scrap irons in such castings. This scrap iron often brings intothe castings such elements as vanadium, molybdenum, chromium, manganese,copper, etc. Iron dust from such castings used in the reduction ofquinones, or as a source of ferrous salts in such reductions introducessome of these elements into the hydroquinone solutions. Many of theseelements facilitate the absorption of atmospheric oxygen and suchsolutions detericrate rapidly. Hydroquinones crystallizing from suchsolutions are brown and have to be recrystallized. Even the color of therecrystallized product and the keeping properties of the finishedcrystals leave much to be desired. Developing solutions made from such aproduct containing even traces of some of these elements have poorstability and exhaust prematurely.

It has now been found that the reduction to the hydroquinone stage maybe readily made with zinc powder in a substantially neutral solutionwithout the difliculties due to t e. introduction of these objectionableelements into the finished crystal. In such a neutral solution theresulting zinc-hydroxide is insoluble, and the products are notcontaminated by a zinc salt. Hydroquinone crystals of sparklingwhiteness, excellent keeping qualities, from which developing solutionshaving longer life may be prepared, are more readily obtainable by theuse of such method.

The reduction may be carried out in the presence of only water, powderedzinc and the quinone or quinhydrone. The reaction proceeds much morereadily, however, in the presence of a small amount of a soluble salt oracid whose anion when combined with zinc produces a salt of appreciablesolubility. The use of large amounts of such salts is normally to beavoided in order to prevent inclusion of large amounts thereof in thehydroquinone mother liquor.

Instead of forming the customary light, flocculent, fioury zinc oxide,the zinc is oxidized during the reaction to a dense zinc hydroxide whichmay be readily filtered off, together with any excess of unreacted zinc,giving an exceptionally pure hydroquinone solution. The hydroxide itselfis of unusual density and may be washed, dried and sold or reclaimed.

Instead of powdered zinc, a powder from a predominantly zinc alloy suchas Zinc and alumi- 1 num, zinc and magnesium or any reactive high zincalloy relatively free from objectionable elements may be employed. Theblue powder, which is produced in the smelting of zinc, may

likewise be used. This powder consists of condensed fumes which weredistilled ofi during the smelting operation and contains appreciablequantities of finely divided zinc metal together with zinc oxide.

It has also been discovered that the reduction may be carried out in thepresence of a soluble salt whose cation is capable of having more thanone valence, providing the higher valent cation is reducible by thezinc, and the lower valent cation is oxidizable by the quinone orquinhydrone. For example, a small amount of a soluble iron salt; such asa ferrous salt, may be added to the reaction mixture. When this is done,the ferrous salt in solution will act on the quinone or quinhydrone and.the metallic zinc. The ferric salts produced by the reaction are thenreduced by the zinc and the cycle is repeated. Other polyvalent metalssuch as tin may likewise be employed.

The following examples will serve further to illustrate my invention:

Example I 80 parts of finely divided zinc and four parts of potassiumchloride are added to a vessel equipped with agitator and containing2000 parts of water. The contents of the vessel are heated to 75centrigade and agitated. To this 220 parts of quinhydrone are addedgradually during the course of an hour. The color of the solution isfirst brown but when the reduction has been completed it has becomealmost colorless. When this has occurred, the solids are filtered offand the hydroquinone solution is then treated in the usual way forcrystal recovery. The yield is almost theoretical.

Example 11 160 parts of blue powder containing 50% finely divided zincmetal and 4 parts of ferrous chloride are added to 2000 parts of water,heated to C., agitated, and parts of benzoquinone added as in Example I.After reduction, the solids are filtered off and the hydroquinonerecovered in the usual manner.

While the foregoing examples serve to illustrate the procedure andquantities used, it is understood that toluquinones, and othersubstituted quinones ortheir quinhydrones in proportionate amounts canbe similarly reduced and that instead of adding these compounds in theirsolid form they can be added in solution or they can be introduced in avapor form to -a cooled hydroquinone solution as described in Patent No.1,987,148 and the resulting solution or mixture reduced with the zincsuspended therein. Also, I do not limit myself to the temperature givenbut lower or higher temperatures may be used, as varying thetemperatures merely affects the speed of the reaction.

Where a salt is added to the solution to: speed up the reaction, anysalt or acid may be used whose anion when joined to zinc will give anappreciably soluble zinc salt. For example, hydrochloric acid, sodiumchloride, or magnesium sulphate may be employed.

Either quinone or quinhydrone may be employed in connection with thezinc, although it is preferred to carry out the reduction withquinhydrone. When quinone is employed, it is believed that thehydroquinone first formed units with the quinone to form quinhydrone andthereafter the reaction proceeds on the quinhydrone.

Theforegoing detailed description has been given for clearness ofunderstanding only, and no unnecessary limitations should be understoodtherefrom, but the appended claims should be construed as broadly aspermissible in view of the prior art.

I claim:

1. The process which comprises reducing a compound of the classconsisting of quinone and quinhydrone in a substantially neutral aqueoussolution to its corresponding hydroquinone in the presence of metalliczinc particles.

2. The method as set forth in claim 1 in which the compound isbenzoquinhydrone.

3. The method as set forth in claim 1 in which the solution alsocontains anions whose zinc salt is soluble.

4. The process which comprises reducing a compound of the classconsisting of quinone and quinhydrone in a substantially neutral aqueoussolution to its corresponding hydroquinone in the presence of metalliczinc particles and a small proportion of a soluble zinc salt.

5. The method as set forth in claim 1 in which the zinc particles are inthe form of blue powder.

6. The method as set forth in claim 4 in which the zinc particles are inthe form of blue powder.

7. The method as set forth in claim 1 in which the zinc particlesinclude predominantly zinc alloys containing other metals of the orderof reactivity of the zinc.

'8. The process which comprises condensing quinone vapors in asubstantially neutral aqueous hydroquinone solution in the presence ofmetallic zinc particles and reducing the solution to hydroquinone.

9. The process which comprises reducing a compound of the classconsisting of quinone and quinhydrone in a substantially neutral aqueoussolution to its corresponding hydroquinone in the presence of metalliczinc and a soluble salt of a polyvalent material, the reduced form ofwhich is oxidized by the compound and the oxidized form of which isreduced by the zinc.

JOSEPH SCHUMACHER.

